Steam generating and superheating and air heating unit



Nov. 18, 1958 1.. w. HELLER 2,860,610

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Original FiledOct. 31, 1946 2 Sheets-Sheet 1 465 2 58 W mm 94 44 7 6 F I J 43 54 M Z892 '88 W2 a 8 22 mo 7226 122b mm g 20 7/2 964. 7/8 84 /20 Z EEK/(1B2 4]24 F |G.l

' IINVENTOR [en 1s Wflel/er BY M... ATTORNEY Nov. 18, 1958 L. w. HELLER2,350,610

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Original FiledOct. 31, 1946 2 Sheets-Sheet 2 INVENTOR F 'G' 3 ZeW/s 7405 67/92 MATTORNEY United States Patent ()fiice 2,860,610 Patented Nov. 18

STEAM GENERATING AND SUPERHEATING AND AIR HEATING UNIT Lewis W. Heller,Yardley, Pa., assignor to The Babcock .& Wilcox Company, New York, N.'17., a corporation of New Jersey Original application October 31, 1946,Serial No. 706,926, now Patent No. 2,653,447, dated September 29, 1 953.Divided and this application September 23, 1953, Serial No. 381,813

7 Claims. (Cl. 122-4) division.

The main object of the present invention is the provision of a fuelfired superheated steam generator and air heating unit in which steamsuperheating and high temperature air heating is accomplished byproducts of combustion flowing from a common furnace, while lowtemperature air heating is accomplished by heat transfer from acombination of the products of combustion and super-atmospherictemperature air exhausted from a multiple stage aerodynamic turbineserved by the air heating unit.

A further object is the provision of a fuel fired heat absorbing unitarranged to simultaneously generate and superheat large quantities ofsteam and heat correspondingly large quantities of air under asubstantial superatmospheric pressure, with an air delivery temperatureat 1300 F. or above.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating ad vantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a preferred embodimentof my invention:

Of the drawings:

Fig. 1 is a partly diagrammatic sectional elevation of a heat absorbingunit constructed in accordance with my invention;

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Figs. 3 and 4 are sectional views taken on the lines 3- -3 and 4--4respectively of Fig. 2; and

Fig. 5 is a fragmentary section taken on the line 55 of Fig. 1.

i The fuel fired heat absorbing unit illustrated in the drawings, asused in a binary fluid power plant of the type described, is arranged toreceive a continuous supply of feed waterfrom the regenerative feedwater heating portion of :the steam power plant and one or more streamsof air under super-atmospheric pressure from the discharge of acompressor set, and by the burning of pulverized coal to generate highpressure superheated steam for the steam plant and also heat the airunder a substantial super-atmospheric pressure to a temperature fromwhich expansion to approximately atmospheric pressure will produceuseful power in excess ofthe power requirements of the compressor.

Inasmuch as such a combined steam-air turbine plant requires heated airat or above 1200 F. and advantageously utilizes highly superheated steamin the steam section, the heat absorbing unit is arranged so that theoptimum steam superheat and air temperatures may be attained, throughthe positioning of surfaces with respect to the heat generating furnaceand by the regulation of heating gas flow over the respective surfaces.

In the construction shown by the sectional elevation of Fig. 1, apulverized fuel burning furnace 10 is fired by a plurality of pulverizedfuel burners 12 spaced transversely of the furnace and extending througha secondary air chamber 14 to direct streams of air-borne pulverizedfuel received from one or more pulverizers (not shown) through burnerlines 16, between spaced furnace ,wall cooling tubes 13. The secondarycombustion air is supplied by one or more conduits 20 and is not onlyunder super-atmospheric pressure but at a temperature substantiallyhigher than atmosphere.

The furnace is formed with gas tight fluid cooled walls 22 and a fluidcooled floor 24 adapted to collect and retain a shallow pool of moltenash originating from the fuel and discharging through slag outlet 26.The fluid wall cooling tubes 10 in the present instance are water tubesarranged with water supply connections from and discharge connections toan elevated steam and water drum 23 ofthe boiler. Fluid cooling tubesconveying air or steam may be used in place of some of the water tubesor in combination therewith where radiant heating of the air or steam isdesired.

The furnace 310 extends upwardly, being bounded by the wall tubes and ascreen of tubes 18a positioned across the lateral gas outlet 30 andextendingbetweena junction header 32 and the lower portion of the drum.From the furnace gas outlet a rearwardly extending upright partition 33,formed in part of water tubes, divides the horizontally extendingconvection heating pass into a pair of parallel gas passes 34 and 36.Dampers 37 at the rear end of pass 34 permit regulation of theproportions of the gas flow through each pass. At the rear of thesepasses in which the convection heated tubular elements are located, agas turning space 38 extending transversely of the unit is provided anda downwardly extending gas pass 40 with additional convection heatedelements is arranged to receive heating gases from the horizontal gasflow passes. The walls defining the outer sides of the horizontal gaspasses 34 and 36 and the walls of the turning space 38 are made of a gastight construction adapted to maintain a slightly super-atmosphericpressure within the passes and the space, and they may be advantageouslyconstructed to includeiwater or other fluid heating tubes. The walls ofthe down flow pass are also constructed to retain a pressure aboveatmosphere but as the gas temperatures will be lower, fluid heatingtubes may be used primarily as structural support elements.

Below the downflow gas pass a gas-tight refractory walled .hopper bottomchamber 41 is arranged as a gas turning space, a gas and air mixingchamber and an ash separating and collecting space. A final upflowgaspass is partly formed by a plurality of transversely spaced circular gasoutlet passages 42 opening to the upper rear end of the chamber 41 andeach containing a tubular air heater 43. A common breeching 44 joins thepassages 42 to the casing of a primary air heater 46. From the top gasoutlet of the primary air heater 46, the heating gases originating inthe furnace are delivered through a connector 48 to a stack dischargingto atmosphere.

When a feed water economizer is used to heat the boiler feed water fro-mthe temperature at. which it is discharged from the regenerative heatingsystem of the steam turbine to or approaching the saturated steamtemperature in the drum, such a feed water economizer 50 may be arrangedinthe downflow gas pass 40,,with

the lower inlet header 52 receiving the feed water. The

'economizer consists of a plurality of laterally positioned multipleloop tubular elements extending across the gas pass and connected attheir upper ends to an outlet header 54 which is in turn connected tothe water space of the steam and water drum 28 with the customary flowregulating devices.

Water supply connections from the water space of drum 28 are provided tothe lower headers for the wall tubes 18. Through transverse junctionheader 32 and headers 56 and 58, the convection heated steam generatingtube bank located in gas pass 34 receives a supply of water to the lowerends of its L-shaped tubes 60, as shown in Fig. 3. The upper ends of thefurnace wall and gas pass wall tubes are connected directly or throughsuitable junction headers to deliver steam and water to the drum 28.

The steam which is separated from the water in drum 28 passes throughconnectors 62 to an inlet header 64 of a primary superheater 76consisting of a plurality of multiple loop elements pendantly positionedin gas pass 34 and the steam passing through the elements is collectedto transverse outlet header 68. A connecting pipe 70 joins the outletheader of the primary superheater with the inlet header 72 of asecondary superheater 74 in the gas pass 36. superheater 76 is theregulating superheater while superheater 74 having a much greater amountof heat absorbing surface does the major por tion of the superheating ofthe steam delivered by the the drum. From outlet header 78 a pipe 81)conveys superheated steam to the steam consumers, of which the steamturbine of the combined power plant will utilize the major portion. As ameans of controlling steam temperature in order to prevent overheatingof tubes of the superheater 74 and also for regulating superheated steamdelivery temperature, an atternperator (not shown) may be introducedintermediate the length of the flow paths of the multiple loop tubularelements which form the heat absorbing surface of the secondarysuperheater.

In the heating of air for utilization in the air turbine at asubstantial superatmospheric pressure and a temperature above 1200 F.,heat transfer surface consisting of tubular elements is so arranged thata minimum pressure drop will occur in the passage of the air from theinlet to the low temperature heaters to the air outlet of the hightemperature heater, while at the same time the air heating surfaces areso arranged that they may be economically constructed.

As an alternate construction, the convection superheater 74 may bereplaced as a Whole, or in part, by radiant absorption superheatingelements, in which case the high temperature air heater portion 8612,which will be described hereinafter, will be brought closer to thefurnace and subjected to much higher gas temperatures.

As arranged in the apparatus shown by Fig. 1, the

high pressure air heating surface is divided into low, intermediate andhigh temperature sections which are serially connected for air flow incounterflow relation to the heating gases. The low temperature inletsection is formed by the three upright straight tube heaters 43,receiving air at their upper ends from the discharge of the last stagecompressor with the air flowing about the outside of the gas flow tubesand discharging at the lower end thereof to the inlet manifold of theintermediate section 84, which is formed by a plurality of laterallyspaced multiple loop tubular elements through which the air flows. Thehigh temperature section 86 is in the present instance formed in twoportions, the inlet portion 860 being located in the down gas pass 40directly above the economizer 50 and the serially connected outletportion 86b in the horizontal gas pass 36 at a position rearward ofsuperheater 74. The high pressure air heated to the operatingtemperature by the high temperature section is delivered from outletmani- 4 fold 88 to the inlet of the air turbine for expansion and powergeneration.

The low temperature air heater section is divided into three separatelaterally spaced units 43 for structural reasons inasmuch as they handleair under a substantial superatmospheric pressure. Each unit 43 consistsof a closely spaced bank of upright tubes 90 arranged within a pressurerestraining external metal casing 92 of circular cross-section, thetubes being secured at their upper and lower ends into perforated tubesheets 94 and 96 respectively. The unit is supported from the structuralmembers 98 by a plurality of brackets 100 rigidly connected to thecasing so that any expansion of the casing with increase in temperatureis upward from the level of the supports.

The upper tube sheet 94 is supported from the upper end of the casing 92by a number of circumferentially spaced struts 182 so that the load ofthe tubes pendant from the upper sheet is carried on the casing. Thepressure air inlet to the intertube spaces is formed by a circularbustle 104 of semi-circular section, and the pressure air delivered fromthe compressor through conduit 106 is introduced through a transversemanifold 1118 which has lateral connections 110 to the individualbustles 104. The air enters radially inward and flows downward in thetube bank to an outlet comprising an annular bustle 112 and then throughlateral connections 114 to a common transverse manifold 116 connected tothe air inlet ends of the multiple loop tube elements 118 of theintermediate pressure air heater 84. An expansion joint 120 is annularlyarranged about each outlet opening 42 and connects each outlet with thelower tube sheet 96 of each unit. The gas leaving the outlets 42 entersthe tubes at the lower ends and leaves at, the

upper end of each unit to enter the common transverse breechingconnection 44 which joins the gas outlet streams of the three unitstogether for passage through the primary air heater 46.

As the hot gases flowing in the tubes heat them to a temperature higherthan that experienced by the casing, the differential elongation will betaken care of by the flexing of the lower sector of the annular bustlewhich extends from the outer edge of the circular tube sheet 96. By thisconstruction an air heater can be economically constructed for heatingrelatively large quantities of air under pressures above atmosphere andthe heating surface is so proportioned with respect to the gas flowpassages that plugging of ash, etc. is avoided. The construction alsolends itself to the attainment of good air temperature rise withoutundue air pressure drop from the inlet to the outlet.

The transverse manifold 116 constitutes an inlet chamber to which theplurality of transversely spaced tubular multiple loop air heatingelements 118 of the intermediate heater 84 are connected. Elements 118are of relatively small size and are spaced with intertube spaces togive an effective convection transfer of heat from the downwardlyflowing gases about the tubes. The bank of elements 118 extends fromside to side of the down gas pass 40 as defined by side walls 122a,front wall 122b, and rear wall 1220.

The upper outlet ends of the air heater tubes 118 are individuallyconnected by vertical tube portions 118a located in the gas pass 40 tothe lower inlet ends of the tubes of the high temperature section 86a. Ajunction manifold may be used as an alternate construction but a directtube to tube construction is preferable. The horizontally extendingelements of the section 86a are of reverse bend type and aretransversely spaced between walls 122a of the downflow gas pass 40, theuppermost tube lengths being adjacent the gas turning space 38 andreceiving radiant heat from the gases in that space. The forward airoutlet ends of these tubes connect to a transverse junction manifold 124extending the full Width between walls 122a,

The outlet portion 86b of the high temperature section is made up of aplurality of serially connected vertically extending inverted U-shapedtube lengths 126 receiving air from manifold 124 and delivering heatedair to outlet manifold 88. Tubes 126 are transversely spaced between thesides of the gas pass 36 which is narrower than the downflow gas pass40. The air discharged from manifold 88 is at operating pressure andtemperature and is directed to the air turbine for expansion therein.

Partition 32 separating the horizontal gas flow passes 34 and 36 is madeup of a row of spaced vertical extending water tubes 128 connected intothe circulation of the boiler with intertube space closures ofrefractory held in place in the customary manner. The detail arrangementof the partition is shown by sectional elevation of Fig. 4.

The gas turning space 41 is proportioned to give a reduction in gasvelocity permitting the gravity separation of ash particles forcollection in the lower portion of the hopper bottom and periodicremoval through sealed ash removal conduits 130. Space 41 also providesspace at its rear side adjacent the gas outlets 42 to the lowtemperature air heaters 43, which is adaptable as the zone Z into whichthe bypassed air exhaust from the final stage of the air turbine may bedirected and mixed with the heating gases flowing into space 41 from thedownflow gas pass 40.

The exhaust air bypass from the air turbine is connected to a manifold132 extending transversely within the space 41 at a position laterallyof the gas stream discharged from the downflow gas pass 40. Thismanifold has a plurality of longitudinally spaced discharge nozzles 134constructed to distribute the air from the manifold in a plurality ofseparate streams in mixing relationship with the gas flowing from thedownflow pass subsequent to the reduction in gas velocity which promotesash separation. The nozzles are constructed in a manner to dischargedivided air streams with a minimum of pressure loss.

The primary air heater 46 positioned to receive heating gases from thebreeching connection 44 is a straight tube heater in which the gasesflow through the tubes and the air to be heated fiows on the outside ofthe tubes, the air being received from the primary air blower (notshown) of the system at inlet connection 46a and being discharged afterheating by flowing downward about the tubes to outlet connection 46b.

With a heat absorbing unit consisting of the combination of steam andair heating surface constructed and arranged in a manner similar to theunit shown, it will be possible to produce superheated steam at therequired rate and with the desired degree of superheat temperaturecontrol while at the same time heating air under pressure to atemperature at which it can be used to generate a subiantial amount ofpower. The arrangement provides for the generation of high temperatureheating gases by the burning of pulverized coal under high temperatureash slagging conditions although it is obvious that other types of fuelmay be satisfactorily burned in the furnace to generate the heatinggases,

While in accordance with the provision of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus and. method of operation disclosedwithout departing from the spirit of the invention covered by my claims,and that certain features of my invention may sometimes be used toadvantage without a correspond me f t r f at re What is claimed is;

l, A combined steam generating, steam superheating and air heatingapparatus comprising walls including steam generating tubes forming acasing enclosing a furnace chamber, means for burning fuel in saidfurnace chamber, a plurality of parallel flow heating gas passes openingdirectly to one side of said furnace chamber, steam superheating tubesarranged in one of said gas passes adjacent said furnace chamber, steamsuperheating tubes in a second of said gas passes adjacent said furnacechamber and serially connected to the superheater tubes in said firstgas pass, air heating tubes in said second gas pass rearwardly of saidsuperheating tubes, steam generating tubes in said first gas passrearwardly of said superheating tubes and substantially opposite to saidair heating tubes, and damper means arranged to proportion the heatinggas flow between said gas passes.

2. A combined steam generating, steam superheating and air heatingapparatus comprising walls forming a casing enclosing a furnace chamber,means for burning fuel in said furnace chamber, a plurality of parallelflow heating gas passes opening directly to one side of said furnacechamber, steam superheating tubes arranged in one of said gas passesadjacent said furnace chamber, steam generating tubes in said gas passrearwardly of said superheating tubes, steam superheating tubes in asecond of said gas passes adjacent said furnace chamber and seriallyconnected to the superheater tubes in said first gas pass, air heatingtubes in said second gas pass rearwardly of said superheating tubes,damper means arranged to proportion the heating gas flow between saidgas passes, a common gas turning space arranged rearwardly of said gaspasses, a downflow vertical gas pass opening to said gas turning space,and horizontally extending air heating tubes in said downflow gas passconnected in series with said second pass air heating tubes.

3. A combined steam generating, steam. superheating and air heatingapparatus comprising walls forming a pressure-tight casing enclosing afurnace chamber, means for burning fuel in said furnace chamber, meansfor supplying combustion air under a superatmospheric pressure to saidfurnace chamber, a plurality of parallel flow heating gas passes openingdirectly to one side of said furnace chamber, vertically extending steamsuperheating tubes arranged in one of said gas passes adjacent saidfurnace chamber, vertically extending steam generating tubes in said gaspass rearwardly of said superheating tubes, vertically extending steamsuperheating tubes in a second of said gas passes adjacent said furnacechamber and serially connected to the superheater tubes in said firstgas pass, vertically extending air heating tubes in said second gas passrearwardly of said superheating tubes, and damper means arranged toproportion the heating gas flow between said gas passes.

4. A combined steam generating, steam superheating and air heatingapparatus comprising walls forming a pressure-tight casing enclosing afurnace chamber, means for burning fuel in said furnace chamber, meansfor supplying combustion air under a superatmospheric pressure to saidfurnace chamber, a plurality of parallel flow heating gas passes openingdirectly to one side of said furnace chamber, vertically extending steamsuperheating tubes arranged in one of said gas passes adjacent saidfurnace chamber, vertically extending steam generating tubes in said gaspass rearwardly of said superheating tubes, vertically extending steamsuperheating tubes in a second of said gas passes adjacent said furnacechamher and serially connected to the superheater tubes in said firstgas pass, vertically extending air heating tubes in said second gas passrearwardly of said superheating tubes, damper means arranged toproportion the heating gas flow between said gas passes, a common gasturning space arranged rearwardly of said gas passes, a downflowvertical gas pass opening to said gas turning space, and horizontallyextending air heating tubes in said downflow gas pass connected inseries with said secondpass air heating tubes.

5. A combined steam generating, steam superheating and air heatingapparatus comprising walls forming a.

pressure-tight casing enclosing .a furnace chamber, means for burningfuel in said furnace chamber, means for supplying combustion air under asuperatmospheric pressure to said furnace chamber, a plurality ofparallel flow heating gas passes opening directly to one side of saidfurnace chamber, vertically extending steam superheating tubes arrangedin one of said gas passes adjacent said furnace chamber, verticallyextending steam generating tubes in said gas pass rearwardly of saidsuperheating tubes, vertically extending steam superheating tubes in asecond of said gas passes adjacent said furnace chamber and seriallyconnected to the superheater tubes in said first gas pass, verticallyextending air heating tubes in said second gas pass rearwardly of saidsuperheating tubes, damper means arranged to proportion the heating gasflow between said gas passes, a common gas turning space arrangedrearwardly of said gas passes, a downflow vertical gas pass opening tosaid gas turning space, horizontally extending air heating tubes in saiddownflow gas pass connected in series with said second pass air heatingtubes, a second gas turning space below said downflow gas pass, meansfor introducing a heated gas under a superatmospheric pressure into saidsecond gas turning space concurrent with the heating gas flow therein, aplurality of parallel flow fluid-tight passages opening to said secondgas turning space and enclosing a multiplicity of vertical heating gasconduits, and means for passing air under a superatmospheric pressurethrough said passages around said heating gas conduits and seriallythrough said horizon tally and vertically extending air heating tubes.

6. A combined steam generating and air heating apparatus comprisingwalls forming a casing enclosing a furnace chamber, means for burningfuel in said furnace chamber, a heating gas pass opening directly to oneside of said furnace chamber, steam superheating tubes arranged in saidgas pass adjacent said furnace chamber, steam generating tubes in saidgas pass rearwardly of said superheating tubes, air heating tubes insaid gas pass rearwardly of said superheating tubes, a fluid-tightpassage connected to said gas pass, a multiplicity of heating gasconduits enclosed by said fluid-tight passage, and means for passing airunder a superatmospheric pressure through said passage around saidheating gas conduits and then through said air heating tubes.

7. A combined steam generating and air heating apparatus comprisingWalls forming a casing enclosing a furnace chamber, means for burningfuel in said furnace chamber, a heating gas pass opening directly to oneside of said furnace chamber, vertically extending steam superheatingtubes arranged in said gas pass adjacent said furnace chamber,vertically extending steam generating tubes in said gas pass rearwardlyof said superheating tubes, vertically extending air heating tubes insaid gas pass rearwardly of said superheating tubes, a common gasturning space arranged rearwardly of said gas pass, a downflow verticalgas pass opening to said gas turning space, horizontally extending airheating tubes in said downflow gas pass connected in series with saidvertically extending air heating tubes, a plurality of parallel flowfluid-tight passages connected to said downflow gas pass, a multiplicityof vertical heating gas conduits en- .closed by each of said fluid-tightpassages, and means for passing air under a superatmospheric pressurethrough said passages around said'heating gas conduits and then ser1al1ythrough said horizontally and vertically extend- .ing air heating tubes.

References Cited in the file of this patent UNITED STATES PATENTS1,814,010 Snow July 14, 1931 1,872,138 Grady Aug. 16, 1932 1,878,908Steinmuller Sept, 20, 1932 2,196,889 Bailey Apr. 9, 1940 2,357,300Bailey Sept. 5, 1944 2,385,177 Wiederkehr Sept. 18, 1945 2,486,291 KauerOct. 25, 1949 2,539,255 Kauer et a1. Jan. 23, 1951 FOREIGN PATENTS257,770 Germany 'Mar. 20, 1913

